Dare to Repair—Phase 3: Reproduction

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This is one in a series of guides used in our Dare to Repair 3D-Printed Repair Parts Contest. This guide describes the first phase of the project: Decomposition. First-time readers are advised to read the whole guide; experienced readers can use the quicklist in each step to guide.

For more information—including rules, submission guidelines, and prizes— check out our Dare to Repair contest announcement on our blog. Don't forget, your submissions are due on Monday, May 14.

For easy reference, here's a complete list of guides in this series:

The final step in the process is the actual reproduction of the part from the 3D model that you have created. 3D printing is actually really accessible: 3D printers are becoming widely available through public workspaces such as FabLabs, Makerspaces, libraries and various technology-related workspaces. Furthermore, owners of 3D printers can register on platforms such as 3D Hubs, and make their printer available as a paid service! There are also professional 3D printing services, which offer access to industrial machines, materials and superior quality at a cost. We will focus on low-threshold access to desktop 3D printers.

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You will need your computer again to prepare your freshly created 3D model for printing. As you probably already have done, your model should be checked for integrity and exported to the .STL file format. As a result, a triangulated version of your model, consisting of only the surfaces of the volume by means of interconnected triangles, will be the basis for your 3D print.

This model will be ‘sliced’ into the layers and toolpath for the 3D printer, so it knows how to construct your model. You will need special slicer software for this if you are preparing the printing job yourself. If you are printing yourself, you probably want to use Cura for this, unless the printer requires special software (look for this at the respective manufacturer’s website). Cura is free, open-source and compatible with a wide variety of printers. Download it here. If you’ve chosen a printing service, they’ll do the slicing for you.

Local shops, workspaces, libraries, technology-related (educational) organizations or even your neighbour might have a 3D printer. You can also check online if a FabLab or Hackerspace (community-driven workspaces for hobbyists) near you has a 3D printer. These are often available to everyone, for a small fee, as a workshop or under subscription. Ask around! Otherwise, the following online platforms provide information about available printers and printing services nearby.

Another option is to order your 3D print online at a professional 3D printing service. You upload your model on their website, select a material and the part will be delivered to your doorstep in a week or so. Such services often have industrial machines and, therefore, offer different material and superior quality, at a cost. The following services are a couple of the most popular 3D printing services. (Read more about 3D printing services on All3dp.com.)

Before setting out the printing job, make sure that your model is intact and eligible for 3D printing! If you have 3D scanned your part, make sure that you ran an error analysis in Remake.

If you have created the model yourself in CAD, you probably do not have to worry. You can always load the model into your slicer software, and see if it succeeds during import. Also, check if there are any thin parts on your part; they should be at least 1-2 mm thick to be printable. If you are not certain about the printability of your part, take a look at the knowledge base of 3D hubs.

If you are printing at a printing service, upload the model to them, and get advice about your printing job. Some services offer a model integrity check, price quote or even design optimisation.

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Slicing a model in Cura. The ‘Layers’ view shows the toolpath, building up the model’s shell (red and yellow), infill (green) and support material (turquoise).

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A different orientation has a large impact on the print. Although it looks like less support material is needed, the upside down cavities have to be filled with supports as well. The outside of the part is then not affected by contact markings from the support, but the inside is. In this case, it is probably desired to rather have markings on the outside than the inside, as these details are more critical and the support is then more easily removed.

Before printing, the 3D model has to be prepared for the specific printer. Slicing software cuts the model into very thin, printable layers, according to the settings you provide. These layers are then traced in a path for the printer head to follow. This toolpath, along with temperature, extrusion speed and various other settings tell your printer how to print your model! You upload this ‘GCode’ to your particular machine, often via a USB stick or SD card.

Besides printer settings and slicing, slicing software like Cura often contain printing optimisation tools. Three of these are very helpful: support structure, bed adhesion and the infill setting.

  1. Parts are rarely directly printable without any supporting material between the printing bed (the surface the part will be built upon) and any overhanging geometry. If you print layer-upon-layer, you will need a previous layer to print upon. If geometry is floating in the air during printing, support structure is automatically generated by Cura! This additional material is printed in layers as well, but can be broken off easily after printing. It often leaves markings on the connecting part, however.
  2. The first layer of the print is crucial; it has to stick to the bed, or the part will deform from the printing heat. Cura can generate an extra band of material on the first layer, around the contour of the part, that help your part stick to the bed better, called a Brim.
  3. The infill setting in Cura can help reduce the printing time and material cost greatly when you have large, solid volumes. The solid does not have to be printed entirely solid in most cases. Instead you can select a pattern and percentage to which Cura will generate infill to substitute for the otherwise solid printed volume. Generally, infill as low as 20% is strong enough, as the outer ‘shell’ will always be printed solid.

When you load your model into Cura, it will automatically start slicing. If you set the view to ‘Layers’ after it is finished slicing, you can review the toolpath and generated support structures.

In most cases, you will have to re-orient your model to minimize the support structure. Also, be aware of the build direction. As the layers are stacked over the vertical (Z) axis, the part is significantly weaker in this direction. This is due to the layer adherence, which is weaker than the material connections within one layer.

Here are three main things to look for when considering orientation:

  • Lay flat. Keep the part as low to the bed as possible, reducing the support structure to a minimum. Also, prevent overhang above other sections of the part, as this will fill up with support material. Aim for overhang angles of a maximum of 45 degrees.
  • Intricate details on top. As support material will probably affect the visual quality of your part where it makes contact, keep fine details on top.
  • Build direction. If you are printing a mechanical part, try to align the load-bearing features to the XZ plane, so the individual layers rather than the stack will take the forces. Think of a beam, if you print it vertically, it will be a large stack of small layers, eager to snap under load. Instead, print it flat to have the strength of the individual layers over the whole length

You should select a material based on your findings in the decomposition phase. The material you select should align with the part’s functions, otherwise your part will fail or not comply with the initial requirements.

Here’s an online tool that will help you to select an appropriate 3D printing material for your case!

The tool includes five of the most common rigid plastics for desktop printers: PLA, ABS, PET, Nylon and PC. If you’re in doubt about your selection, ask a 3D printing expert. A more elaborate list (and comparison) of 3D printing materials can be found on All3dp.com.

Newer printers can print a model in two materials at once! This is very helpful when you load the material PVA as a secondary: PVA is an alcohol-based, water-soluble material that can be used to print support structures. You can then simply dissolve the support structure in water, leaving almost no marks on the printed part.

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Now you’ve reached the actual printing job! If you are printing at a service, simply select the right material and upload your model. You will probably get an indication of the cost and time it takes to deliver your product. Good luck!

In case you are printing yourself, get familiar with the printer you’re using (read the owner’s manual!) After slicing your model in Cura, write the Gcode onto an SD card and insert it in the printer. Make sure there is enough material left in the printer, or load a new spool. Start the printer and check in periodically to see if it prints without errors. Especially check the first couple of layers, to ensure that they stick to the printing bed well!

After printing, check for any printing errors, remove any support material with a sharp knife and sanding paper, clean the print with some water and soap and you are probably ready to reinstall your freshly created spare part into your broken product!

If your print is not perfect the first time around, consider the following troubleshooting tips:

  • Is there any material in the way when reinstalling the new part on the product? - See if you can remove any material: drill out holes, cut away material using a sharp knife or sand it down to make it fit.
  • Does your print not fit, connect or line up? - You will have to go back to your model and alter the failing geometry. Consider ‘cutting’ away material and remodeling details that are not fitting. Print again.
  • Is the print too small or large? - Measure a clear reference on your original part and take the exact same measurement on your print. Divide the print’s dimension by the original; this is the scale factor you will have to apply on your model to scale it properly! Print again.
  • Are any details lost, or is the part ugly because of support material? - Consider a different orientation for printing. Intricate details should be facing up, preferably! If you have a bold surface touching the printer bed, consider making it entirely flat to eliminate any support structure underneath. You can also look for a dual extruding printer, that prints the support material in water-soluble PVA!

Hopefully, you have a printed part at the end of this process. Once the part is printed—and you’ve confirmed it works, upload your model onto Shapeways. Then document the installation of your repair part on an iFixit guide—that way everyone can use the resources you created to fix their broken product. Be sure to tag your guide with the Dare to Repair flag on iFixit—so the judges can find your contest submission. (More info about that here.)

For more information about the contest, including rules and prizes—check out the contest page here.


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